1. Field of the Invention
The present invention relates to a system and method for detecting the presence of a thermal ink jet printhead in the event that the primary detection method fails to properly identify an installed printhead.
2. Description of the Related Art
Thermal ink jet printers apply ink to a print medium such as paper by ejecting ink drops from a printhead through an array of nozzles. Each nozzle is associated with a heater resistor that generates heat when sufficient current passes through it to cause ink within an associated ink reservoir to be ejected from the nozzle. The printhead ejects ink as it is passed over the print medium in a series of passes, with the print medium being advanced between passes. A printhead controller determines which resistors will be “fired” and the proper firing sequence so that a desired image can be printed on the medium.
Typically, printheads are in the form of replaceable printhead cartridges, with each printhead cartridge including one or more ink colors. Often, the printhead controller requires the input of information identifying the type of installed cartridge so that the controller can be adjusted for proper printer operation. Various printhead identification schemes and devices are known which operate to provide identification information to the printhead controller, including information relating to cartridge presence and type. One such printhead identification device is described in U.S. Pat. No. 6,161,915 (assigned to the same assignee as the present invention), wherein the printhead identification device is described as being manufactured as part of the printhead cartridge. In general, such devices reliably provide identification information to the controller. However, if the printhead identification device is damaged or improperly manufactured, the controller may deem a cartridge missing, even though it is actually installed and will still print as designed.
Inaccurate detection of printheads is especially problematic in stand-alone All-In-One devices that provide printing, copying, scanning, facsimile services, memory card readers, or some combination of the foregoing functionality. With an all-in-one device, the device itself must make the determination of printhead presence for user feedback. Therefore, another printhead detection scheme is needed to supplement the present identification schemes.